Manufacture of surface-hardened fiberboard



Patented.

NT OFFICE MANUFACTURE OF SURFACE-HARDENED FIBERBOARD Henry E. Walter,Clo net, Mlnm, assignor to Wood Conversion Company, Cloqnet, Minn., acorporation of Delaware No Drawing.

3 Claims.

The present invention relates to the manufactureof artificial fiberboard, and more particularly to one with a hardened surface, which iswater-resistant,.washable, resistant to scar and scuff, yet whichpresents a distinct fibrous texture.

Heretofore, artificial board has beenmade from aqueous slurries of fiberin which water-resistant materials such as drying oils as emulsoids havebeen incorporated. These produce boards which are more Or less uniformthroughout as to the effects of the oil. In order to obtain greatsurface hardness and water resistance, very large amounts of oil areneeded for such a process.

Also, heretofore, attempts have been made to limit the hardening to thesurface by adding drying oil to the surfaces of dry board. Thepenetration is deep, and again, for great surface hardness, too much oilis required. a

The present invention is directed to the pro- Application February 3,1940, Serial'No. 817,105

added with the same oil. I

duction of oil-hardened surfaces with a fibrous texture, using a minimumof oil.

One object of the invention is to apply oil to board in the process ofmanufacture, when the stock for the board, in mat form, is already wetwith water, thus resisting penetration of oil.

Another object of the invention is to apply oil to wet-board-formingmats in the form of an oil-in-water emulsion, further to limit thepenetration of oil.

Still another object of the invention is to add drier to the oil, and todry? the board and harden the oil simultaneously by the application ofheat in the presence of oxygen in such a way as to eifectsetting of theoil while the board is still wet and in process of drying.

The invention may be carried out in numerous ways, and with numerousmaterials. Vegetable oils are known in both drying and non-drying form.Recently, drying oils have been made from non-drying vegetable oils,such as dehydroxylated castor oil, and also from petroleum and otherhydrocarbon bases, such as Puro-Resin, a trademarked product which is anunsaturated petroleum derivative having double bonds in the moleculewhich dry as do the double bonds in dry-, ing oils, giving an oxidizedsolid resin-like product. These and the natural drying oils, such as IPerilla, linseed, soya bean, China-wood, oiticica,

and many others, may be used. They are emulsified in water with aminimum of other material, except emulsifying agent and drier.Incorporation of other solids, for example starch, merely adds filler toabsorb oil. The preferred absorbent forthe oil is the surface layers ofthe The following composition is a suitable one to illustrate theinvention:

Percent by weight Water I 69.4 China-wood oil 27.8 Japan drier 2. Sodiumcarbonate .4 Dyestuffs (for coloring) .4

Water, 011 and drier are the chief constituents, and the proportion ofeach is not at all critical. They are used in such proportions as'willprovide a stable useful emulsion for the practical method of applicationadopted. The choice of an emulsifying agent, such as the sodiumcarbonate has some place in determining the oil concentration, where alow content of agent is used. Compounding is efiected largely withreference to oil usage and consistency of emulsion for the particularmethod of application. In the above example the sodium carbonate andwater at to F. are used as a vehicle to receivethe mixed drier and oilwith emulsifying agitation. The emulsion may be sprayed or roll-coatedonto a wet mat of fibers.

In making board theslurry of fibers, as of wood or other vegetable form,is ordinarily flowed onto a wire, through which water drains. The wetmat passes through squeeze rolls or other press to remove excess waterand provide a mat capable 01 being dried with or without pressure toprovide a board. Such a wet mat may be used as a base to receive theemulsion as a surface coat. The mat may .then be dried directly afterreceipt of the emulsion, or it 'may be subjected to further pressing.However, for the economic limitation of penetration it is preferred todry it without pressing sion.

Where the board is treated to mark its surface, as by a marking net, asdescribed in my application Serial No. 220,355, filed July 20, 1938, now

Patent No. 2,369,092, issued February 6, 1945, the preferred pointof'applying the emulsion depends upon the manner of application. A netof loose heavy cordsextending generally parallel, tied is pulled taut,and the cords lie haphazardly to make a pleasing non-repetitive pattern.This device, or any other impression device, is forced into a wet matpermanently to deform the surface,

without destroying a continuous felted connection betweenthe surfacefibers. An open mesh after applying the oil em'ul-- 1 bath, principallyto backing sheet. of fabric may be used for mounting the cords, or anyother impression members. In such case, a felt may be used in back ofthe fabric to absorb surface of 'the mat matis being continuouslyformed, as in a Four-.

any water expressed from the being marked. Where thedrinier type ofmachine, a flexible impression device and felt, in endless belt form arepreferred.

The returning stretch of the marking'device may as by running through acleaning prevent accumulation ofso1- ids-and fibers by continuous use.Squeeze {rolls provide the marking pressure. In a machine coinbiningstructures such Patent No. 1,690,152 and Streeter No. 1,712,852, themarking device and the felt need not be flexible for use in the fiatplaten press of Ziska.

A net capable of forming a multitude of wavy becleansed,

grooves running close'together'f in the same general direction, is apatterffbvhich may be successfully coated with aidl'l', afterimpression, with an emulsion of oil to produce a uniformly toughsurface- The'final board after drying and surface flattening exhibitsintaglio depressionsfrom .005- to .04 incht deep, with a predominantdepth from tion. The surface described in detail is rollcoated inpractice with the composition as given. Hence it is not necessary toapply the emulsion before forming depression or intaglio designs on themat. It is preferred to apply the emulsion after the formation ofimpressions or intaglio designs, in order to avoid removing emulsion inthe marking step. Such a mat marked or plain, with oil emulsion coatedthereon, is passed into an oven for drying, wherein air is present, thetemperature .being well above 212 F. to boil out the water in the mat. Acommon temperature range is from 310 Fhto 345 F., and in some cases itis common to have fiat platens or feet to contact the board as it dries,thus to reduce the high parts thereof to a common level or callper, asdescribed in Frost No. 2,154,201.. A high heat of the oven isparticularly desirable in order that the direct heat of the oven or theplatens hasten the setting of the oil by oxidation before the boardinside is dry. Thus the oil is localized and set at the surface to givemost efficient use of oil.

The desired oil-skin effect on a boardof density about 16-pound per cu.ft. with a hi h degree of localization, begins at about 7 pounds of oilper 1000 sq. ft. It may be used up to 30 pounds of oil per 1000 sq. ft.Common practice for uniform results calls 'for a usage from 11 to 22pounds, with preference for lowest usages in that range.

' Usage below 7 lbs. per 1000 sq. ft. fails to give sufficient depth tothe skin for practical resistances in Wainscot uses.

The board presents a fibrous texture, rather than an oil-skin texture,but it has properties akin to an oil-skin. The surface fibers areoil-sized and bound together by the dried oil. The surface is free fromfuzz. It is water-resistant, washable like paint, hard, and resistant tomaras shown in th Ziska ring and scufiing. It is excellent for use asWainscot, and in this use it is desirably decorated with impressions asset forth in my said prior applications. The usage Ofoilis verylow, andthe maximum benefit of th I-oil." btained'. The process describedpermits somerset penetration to give more than a thin shell at thesurface of the board. The penetration may be modified by many changesin-co'nditions, and the thickness of the hardened layer may be increasedbya greater quantity of oil.

Any desired color may be obtained by. addin dyestuffs, eitheroil-soluble or water-soluble, to color the oil, or to color the fibers,or both. Pigments and fillers are preferably absent since they tend tofilter out on the fibers to coat them,

I and may be rubbed oif in cleaning operations.

The'oil and 'color at the surfac enter the fibers and the oil hardensthe fibers. individually and as afelt.

A variant of the invention forboards' already made is to wet the boardwith water at the surface to be hardened, then to apply the emulsion,and then subject to heat toharden the oil and dry out the water. Theapplication to wet board prevents striking in of oil, and the use of anemulsion gives uniform distribution of the oil,

' which otherwise would be repelled by the wet oil over the surface.

.. companying claims.

fibers. The drying of the oil is to be effected before the drying of theunder-layers of fibers.

in order to prevent striking in of the oil. This is simply accomplishedby the use of boiling drying temperatures, and by the use of driers inaccordance with the needs of the oil selected.

The compounding of the emulsion is of course effected to include a highcontent of oil, thereby in part to limit the amount'of water to be driedout, and in part to provide a suitable thick emulsion to give a uniformdistribution of the In forming a felt the fibers of surface layer and ofthe wire-face are in continuous felted relation. The impression of adesign with depressions into a wet mat preserves this continuous feltedlayer. The presence of oil in the layer with or without a design makes acontinuous resistant surface. Heretofore, designs have been cut intodry, fiber boards, but this breaks the surface continuity-of the web andexposes fiber ends at the under-cut parts. Where the entire surface witha design is to present uniform resistant properties, it is veryimportant that the hardening agent and the design be applied while theboard is wet and while the continuous felted connections at the surfaceare shiftable, and then to dry the mat to set the surface connections,and hence the design, and also to set the hardening agent.

The oil-surface snakes an excellent base for paints, varnishes orlacquers, acting as a size to prevent penetration of such coatingmaterials.

Thus, where it is desired 'to'redecorate a board and economically.

vention, and these are contemplated in the ac- Iclaim: pg '1. The methodof making an a" tificialfiber insulation board which comprises..,;forming ,a slurry of vegetable fibers into a wetin'at, squeezingwater from the mat to form' a wet-'insula tion-board-forming mat,applying an emulsion in water of dispersed liquid phase-consisting sub-Various changes and modifications will be 'apparent from the foregoingdescription of the in--' with the wet mat, thereafter exposing the setoil to an oil-hardening atmosphere while effecting hardening of the oiland while continuing the drying of the mat as to water, and completingthe drying of the mat as to water,. whereby the hardened oil islocalized at the surface of the dry mat.

, 2. The method of making an artificial fiber insulation board whichcomprises forming a slurry of vegetable fibers into a wet mat, squeezingwater from the mat to form a wet-insulation-boardforming mat, applyingan'emulsion in water of dispersed liquid phase consisting substantiallyentirely of a setting and hardenable drying oil together with a smallquantity of drier therefor tothe surface of the wet mat in quantity touse 'I to BQ pounds of said oil to 1000 sq. ft. of mat surface, heatingthe wet coated mat in the presence ofan oil-drying and oil-settingatmosphere at a temperature in excess of the boiling point of water andboiling water out of the coatin and themat while pressing mechanicallyon the coated wet mat to reduce the overall thickness mere drying of thewet-surfaced mat produces I of the resulting board to a uniform'caiiper,and

while eflecting setting of the oil to a non-flowing the Wet mat,thereafter condition in contact with exposing the set oil to anoil-hardening atmosphere while eflfecting hardening of thefoil and whilecontinuing the drying ofthe mat as to water, and completing the dryingof the mat as to water, whereby the hardened oilis localized at thesurface of the dry mat.

3. The method of producing a coated board which comprises applying tothe wet surface of a mat of vegetable fibers of character such that avegetable flber board, an emulsion in water of dispersed liquid phaseconsisting substantially entirely of a setting and hardenable drying oiltogether with a small quantity of drier therefor in quantity of emulsionto provide from '7 to 30 poundsof oil per 1000 sq. ft. of surface-of themat, subjecting the coated surface of the mat to a boiling heat in thepresence of oil-setting atmosphere while removing water from the coatingand eflecting setting of oil to anon-flowing condition in contact withthe wet surface of the mat, and continuing exposureof the said oil to anoil-hardening atmosphere while effecting hardening of the oil, andcompleting the drying of the mat as to water after the setting of theoil, whereby to produce a dry board with said hardened oil as a coatlocalized at-the surface of the mat.

HENRY E. WALTER.

